I'd be tempted to buy the guides if they were normally $4.99 to $9.99 but only because it'd then be cheaper than importing the actual book version. Still, the advantage to the digital versions is that they can, theoretically, be updated to reflect current changes to the game in question.

The reason that the manuals are so small now isn't because the companies just want to rip you off. Thats so ridiculous. The reason is because its not necessary. Back when games had more technical limits, the companies relied on the manuals to explain things to the gamer that they could not program into the game. Nowadays, we have extensive tutorials that explain how to play, and beautiful cutscenes that provide backstory. Sure, it might not have the charm of reading poorly-written prose, but it still does its part well (for the most part). I would even argue that it has made the story-telling part of a game purer, as it relies more on the game to convey story and less on the manual.
As for game guides on steam, kudos to prima. I wish them all the luck selling them there. Obviously, hardcore gamers are not going to buy these guides. Still, its not like having them on steam is hurting anyone.

That and most people these days seem like they can't even be arsed to read the manual. So why bother making it any larger than it absolutely has to be when it's not going to be read by the majority? That's just a waste of money in the long run.

Perhaps you'd like to read my post first? Most strategy games don't have the info in the game nor in the manual so explain to me why there's a convenient strategy guide that DOES contain all the info yet according to you, it's not needed despite the fact that games of yore had all the info you could want in their manual?
Here's a hint: games which are completely explained in the tutorial don't HAVE strategy guides. Games which only have the basics shown often DO have strategy guides and a weak manual. Read. First. Then. Reply.

How about you give us an example to prove your argument?

I think strategy guides can be extremely helpful. I also think that you can get the same thing for free on just about any serious game-related site.

Just a warning. The Steam versions of these guides require that you own the game on Steam to use them. Despite the fact that Valve are selling them to people who don't own the games and in regions where the games are regionally restricted. Should have known this was just another attempt of Valve's to scam people.

From the steam forums
"Sorry Valve. Did you even read the guide to your own game? How can you endorse something so poorly written? Did you not hold Prima up to any sort of standard? Perhaps you should be pressuring them to fix the following errors...
Infected
* Charger - Weaknesses: Has difficultly turning once a charge starts; lumbering in enclosed areas; charge takes a long time to build back up (He can't turn!)
* Charger - The charge itself is a straight-line rampage. You have very limiting steering to the left and right (Again, the Charger cannot turn!)
* Jockey - Strengths: Flexible and chaotic attack, with option to stop in mid-ride. (What!?)
* Jockey - You can stop a steering by leaping off the victim if you wish, but this usually results in your being shot as you try and scamper away. (What!?)
* Tank - The burning Tank speeds up, but collapses and die in about 30 seconds. Firing doesn’t kill it off any quicker, so avoid its flailing and concentrate on other threats.(WRONG WRONG WRONG! All wrong! Fire does damage, it's not on a timer anymore!)
* Road Crew - Strengths: Wear niose-muffling head gear, and therefore immune to Pipe Bombs. (Also immune to Bile Bombs)
Pickups
* First Aid Kit - When you administer the First Aid Kit, you are prone and almost immobile (you can walk very slowly) for around 4 seconds, so request cover from a teammate. First Aid can be given to a wounded teammate (who can provide the cover for you, but can’t move faster than a stroll). Around 60 points of the Health you have lost is restored when you use a First Aid Kit, up to a maximum of nearly 100 Health. (It restores 80% of lost health, not a flat 60, and you CANNOT move will healing! What is this!?)
* Adrenaline - Jab a syringe into yourself to instantly receive a +25 Health boost, slight tunnel vision, and a sharp view of your surroundings. This boost gradually diminishes, but can take your Health over 100. (Health gains stop at 99)
* Pills - When taken, Pain Pills add up to 60 points to your Health (the exact number depends on the game’s difficulty). Any mobility issues are not healed (False. You get 50 temp health regardless of difficulty, and your mobility issues are temporarily fixed.)
* Incendiary/Explosive Ammo - The next 10 Shotgun shots or 50 bullets are incendiary, meaning they immediately set a target on fire, burning with the ferocity of a Molotov or exploding Fuel Can. Fire can be transferred to other nearby Infected too. This helps nullify large numbers of Common Infected, as well as Special Infected. (Wrong. It gives you a full magazine, not a set number of shots, and the fire doesn't spread)
I haven't read everything, but what I HAVE read so far is just appalling. How is this 100% developer approved with this factually wrong information on some of the most critical aspects of the game? I know Prima doesn't always write perfect guides (often far from it) but this is just a stupid thing to endorse.
On the upside, I knew what to expect when I sunk my $10 into the purchase. I just didn't know how utterly bad it would be. GG Valve.
I will be updating the Original Post as I find more and more errors."
-Arion

Every strategy guide I ever read had those kinds of errors... those writers are usually on an amazing time crunch and they make mistakes. Developers probably don't really proof-read it thoroughly because... well... who cares, and they have limited pre-release time on their hands.

Well, lets see if one of the possible upsides of digital guides are put to use and the guides are updated.
If not, then paid digital guides are not worth a penny of my money and i'll stick with my lovely meatspace guides.

Well, to be fair... Pressing Shift + Tab to show a strategy guide for a game is a pretty awesome idea.
20 dollar is very steep, 10 dollars is alright, but it really should come free with the game. Although, I could see Steam giving away the guides for free with a preorder. Since they usually give away a free game with preorders.
Edit:
@Raneman25
Aren't those guides written by people with old versions of the game? The guides are usually released with the game, so I could see some errors coming from the tweaks the developers made before the game came out. Although, I could be wrong!

guess the guides will be bought by the same people who paid 15 euro for 5 maps for modern warfare 2.
the price for the guides are really idiotic. instead of buying some silly guide off steam, you can visit gamefaqs and have the same thing for free :)

I'll probably buy a guide every once in a while. Convenience beats everything as long as you have the money, right? Not for games like L4D2 or MW2 obviously, but for larger, more complex titles like DA:O, Fallout 3, etc, guides do have their use.
I'm not paying for MW2 maps though. That's a completely different league of money wasting.

right you are then, mate. Fallout 3 and Dragon Age: Origins are huge games with lots of content and a guide would come in handy. the thing is that it's too expensive for me (as a regular guy who lives in Poland).
btw. it's really interesting that the map pack for MW2 sold pretty well, despite the price...